Packet communications have evolved to a point where voice sessions, or calls, can be supported with essentially the same quality of service as provided by circuit-switched communications. Packet communications are generally supported over packet subsystems, which were initially supported by local area networks, but are now supported by wireless local area networks (WLANs). Using WLAN access, user elements can support voice sessions using packet communications while moving throughout the WLAN. As such, WLAN access provides users the same freedom of movement within a WLAN as cellular access provides users within a cellular environment.
In many instances, the coverage areas provided by WLANs and cellular networks are complementary. For example, a WLAN may be established within a building complex in which cellular coverage is limited. Given the localized nature of WLAN coverage, cellular networks could bridge the coverage gaps between WLANs. Unfortunately, WLAN access technology is independent of cellular access technology. Cellular networks generally support circuit-switched communications, and WLANs support packet communications. As such, user elements have been developed to support both cellular and WLAN communications using different communication interfaces. With these user elements, users can establish calls via the cellular network and WLAN using the respective communication interfaces; however, establishing and controlling calls in a first domain is difficult when a user element is homed to a second domain. Further, once such calls are established, there is at best limited ability to maintain control over the calls and to provide services associated with the calls.
Accordingly, there is a need for a technique to effectively and efficiently establish calls for a user element over both cellular networks and WLANs as well as provide seamless control for established calls between the respective domains.